MADRID, Spain (CNN) -- Police arrested 13 men in Barcelona and Valencia early Tuesday on suspicion of working in an international document forgery ring, possibly with links to Islamic terrorists, a police statement said.
Spanish police detain a suspect following the arrests in Valencia and Barcelona Tuesday.
"There are arrests. The police have to determine who is who," a government source told CNN.
The suspects include 11 Pakistani nationals, an Indian and a Nigerian. Most of the arrests were in Barcelona, Spain's second-largest city, but two were in Valencia, the third-largest city, also on the Mediterranean coast, south of Barcelona, the police statement said.
The ring, in addition to providing forged passports, also trafficked in drugs and human beings, in a network stretching to Britain, France, Germany, Belgium, Switzerland and Thailand, and police in those countries were part of the investigation, the statement said.
The ring operated by stealing passports in various Spanish cities and sending them to Thailand, where they were altered and sent to the other five European countries to criminal networks, to facilitate fraudulent border crossings.
Investigators in all of the countries involved were now searching for links between the passport forgery ring and Islamic terrorists, the statement said.
Police searches of locales in Barcelona and Valencia turned up material to forge documents, dozens of passports, some already forged and others blank and waiting to be filled in, passport-sized photographs of numerous people, computer information and cell phones.
Police did not mention finding any weapons or explosives in their searches.
The operation was coordinated by a judge at Spain's anti-terrorism National Court in Madrid.